add failing driver and server tests for circular objs over websocket

packages/driver/test/cypress/integration/cypress/cypress_spec.coffee

@@ -47,6 +47,18 @@ describe "driver/src/cypress/index", ->
 
         done()
 
+    ## https://github.com/cypress-io/cypress/issues/4346
+    it "can complete if a circular reference is sent", ->
+      foo = {
+        bar: {}
+      }
+
+      foo.bar.baz = foo
+
+      Cypress.backend("foo", foo)
+      .catch (e) ->
+        expect(e.message).to.eq('You requested a backend event we cannot handle: foo')
+
   context ".isCy", ->
     it "returns true on cy, cy chainable", ->
       expect(Cypress.isCy(cy)).to.be.true
@@ -75,4 +87,4 @@ describe "driver/src/cypress/index", ->
       fn = ->
         Cypress.log({ message: 'My Log' })
 
-      expect(fn).to.not.throw()
+      expect(fn).to.not.throw()

packages/server/test/unit/socket_spec.coffee

@@ -70,6 +70,22 @@ describe "lib/socket", ->
     afterEach ->
       @client.disconnect()
 
+    ## https://github.com/cypress-io/cypress/issues/4346
+    it "can emit a circular object without crashing", (done) ->
+      foo = {
+        bar: {}
+      }
+
+      foo.bar.baz = foo
+
+      ## going to stub exec here just so we have something that we can
+      ## control the resolved value of
+      sinon.stub(exec, 'run').resolves(foo)
+
+      @client.emit "backend:request", "exec", "quuz", (res) ->
+        expect(res).to.deep.eq(foo)
+        done()
+
     context "on(automation:request)", ->
       describe "#onAutomation", ->
         before ->

packages/server/timerfuzz.js

@@ -0,0 +1,37 @@
+const _ = require('lodash')
+const percentile = require('percentile')
+
+// require('./timers/parent').fix()
+console.log('running fuzz')
+const N = 10000
+
+let differences = []
+
+_.times(N, () => {
+  const ms = 50 + (Math.random() * 1000) // between 0 and 1 minute
+  const started = new Date
+
+  setTimeout(() => {
+    const elapsed = new Date - started
+    const difference = elapsed - ms
+
+    differences.push(difference)
+
+    //console.log(`Expected: ${ms}ms\tActual: ${elapsed}ms\tDifference: ${difference}ms`)
+
+    if (differences.length === N) {
+      printSummary()
+    }
+  }, ms)
+})
+
+function printSummary () {
+  console.log(`Node version: ${process.versions.node}\tElectron version: ${process.versions.electron}`)
+  console.log(`IPC timers? ${global.timersFix ? 'yes' : 'no'}`)
+
+  ;[.1, 1, 10, 20, 30, 40, 50, 60, 70, 80, 90, 95, 98, 99, 99.5, 99.7, 100].forEach((p) => {
+    const q = percentile(p, differences)
+
+    console.log(`${p}%\t of setTimeout calls finished with less than ${q}ms\t of difference`)
+  })
+}